Generally, the etching of a substrate material, such as a silicon material, has been extensively utilized in the formation of various structures on the substrate and in the overall manufacturing of semiconductor devices. Such etching generally utilizes a photolithographic masking and etching process. In such a process a photoresist or hard mask is formed on the surface of the substrate and patterned in order to expose a portion of the substrate. Once the photoresist or hard mask has been placed and patterned, the underlying substrate that has been exposed by the hard mask or photoresist is exposed to an etchant by physically applying an etchant or etching solution to the exposed substrate.
Once in contact with the exposed portions of the substrate, the etchant or etching solution will begin to chemically react with the portions of the exposed substrate in which the etchant or etching solution is in contact. This chemical reaction chemically alters the exposed surface of the substrate and removes portions of the substrate from the surface of the substrate, thereby etching into the substrate as the chemical reaction proceeds. Because of the hard mask or photoresist, and the selectivity of the etchant or etching solution to the material of the substrate over the material of the hard mask or photoresist, the removal of material is controlled to occur only in those areas of the substrate that are uncovered and exposed by the hard mask or photoresist.
However, each etchant that may be utilized to remove material and form an opening into a material of a substrate, and each etching solution that may be utilized, have various benefits and problems. These include achieving a desired selectivity, obtaining a suitable process controllability, or even limiting the potential drawbacks of the etchant or etching solution.
Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale.